/**
 * @file mave.c
 * @note Copyright (C) 2011 Richard Cochran <richardcochran@gmail.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
#include <stdlib.h>
#include <string.h>

#include "mave.h"
#include "filter_private.h"

// 定义mave结构体，用于存储移动平均的相关信息。
struct mave {
    struct filter filter; // 过滤器接口。
    int cnt; // 当前存储的样本数量。
    int len; // 过滤器长度，即移动平均计算的样本容量。
    int index; // 循环缓冲区的当前索引。
    tmv_t sum; // 当前样本的总和。
    tmv_t *val; // 存储样本值的循环缓冲区。
};

// 销毁mave过滤器的函数。
static void mave_destroy(struct filter *filter) {
    struct mave *m = container_of(filter, struct mave, filter);
    free(m->val); // 释放val数组。
    free(m); // 释放mave结构体本身。
}

// 计算并添加新样本的函数。
static tmv_t mave_accumulate(struct filter *filter, tmv_t val) {
    struct mave *m = container_of(filter, struct mave, filter);

    // 从总和中减去即将被替换的样本值。
    m->sum = tmv_sub(m->sum, m->val[m->index]);

    // 更新循环缓冲区中的样本值。
    m->val[m->index] = val;

    // 更新循环缓冲区的索引。
    m->index = (1 + m->index) % m->len;

    // 将新样本值加到总和中。
    m->sum = tmv_add(m->sum, val);

    // 如果样本数量小于过滤器长度，增加样本计数。
    if (m->cnt < m->len) {
        m->cnt++;
    }

    // 返回平均值。
    return tmv_div(m->sum, m->cnt);
}

static void mave_reset(struct filter *filter)
{
	struct mave *m = container_of(filter, struct mave, filter);

	m->cnt = 0;
	m->index = 0;
	m->sum = 0;
	memset(m->val, 0, m->len * sizeof(*m->val));
}

struct filter *mave_create(int length)
{
	struct mave *m;
	m = calloc(1, sizeof(*m));
	if (!m) {
		return NULL;
	}
	m->filter.destroy = mave_destroy;
	m->filter.sample = mave_accumulate;
	m->filter.reset = mave_reset;
	m->val = calloc(1, length * sizeof(*m->val));
	if (!m->val) {
		free(m);
		return NULL;
	}
	m->len = length;
	return &m->filter;
}
